trezor-firmware/tools/binctl

#!/usr/bin/env python3

from __future__ import print_function

import sys
import struct
import binascii

import pyblake2

from trezorlib import ed25519raw, ed25519cosi


def format_sigmask(sigmask):
    bits = [str(b + 1) if sigmask & (1 << b) else '.' for b in range(8)]
    return '0x%02x = [%s]' % (sigmask, ' '.join(bits))


# bootloader/firmware headers specification: https://github.com/trezor/trezor-core/blob/master/docs/bootloader.md

IMAGE_HEADER_SIZE = 1024
IMAGE_SIG_SIZE    = 65
IMAGE_CHUNK_SIZE  = 128 * 1024


class BinImage(object):

    def __init__(self, data, magic, max_size):
        header = struct.unpack('<4sIIIBBBB12s512s415sB64s', data[:IMAGE_HEADER_SIZE])
        self.magic, \
        self.hdrlen, \
        self.expiry, \
        self.codelen, \
        self.vmajor, \
        self.vminor, \
        self.vpatch, \
        self.vbuild, \
        self.reserved1, \
        self.hashes, \
        self.reserved2, \
        self.sigmask, \
        self.sig = header
        assert self.magic == magic
        assert self.hdrlen == IMAGE_HEADER_SIZE
        total_len = self.hdrlen + self.codelen
        assert total_len % 512 == 0
        assert total_len >= 4 * 1024
        assert total_len <= max_size
        assert self.reserved1 == 12 * b'\x00'
        assert self.reserved2 == 415 * b'\x00'
        self.code = data[self.hdrlen:]
        assert len(self.code) == self.codelen

    def print(self):
        if self.magic == b'TRZF':
            print('TREZOR Firmware Image')
            total_len = self.vhdrlen + self.hdrlen + self.codelen
        elif self.magic == b'TRZB':
            print('TREZOR Bootloader Image')
            total_len = self.hdrlen + self.codelen
        else:
            print('TREZOR Unknown Image')
        print('  * magic   :', self.magic.decode())
        print('  * hdrlen  :', self.hdrlen)
        print('  * expiry  :', self.expiry)
        print('  * codelen :', self.codelen)
        print('  * version : %d.%d.%d.%d' % (self.vmajor, self.vminor, self.vpatch, self.vbuild))
        print('  * hashes: %s' % ('OK' if self.check_hashes() else 'INCORRECT'))
        for i in range(16):
            print('    - %02d : %s' % (i, binascii.hexlify(self.hashes[i * 32:i * 32 + 32]).decode()))
        print('  * sigmask :', format_sigmask(self.sigmask))
        print('  * sig     :', binascii.hexlify(self.sig).decode())
        print('  * total   : %d bytes' % total_len)
        print()

    def compute_hashes(self):
        hashes = b''
        for i in range(16):
            if i == 0:
                d = self.code[:IMAGE_CHUNK_SIZE - IMAGE_HEADER_SIZE]
            else:
                s = IMAGE_CHUNK_SIZE - IMAGE_HEADER_SIZE + (i - 1) * IMAGE_CHUNK_SIZE
                d = self.code[s:s + IMAGE_CHUNK_SIZE]
            if len(d) > 0:
                h = pyblake2.blake2s(d).digest()
            else:
                h = 32 * b'\x00'
            hashes += h
        return hashes

    def check_hashes(self):
        return self.hashes == self.compute_hashes()

    def update_hashes(self):
        self.hashes = self.compute_hashes()

    def serialize_header(self, sig=True):
        header = struct.pack('<4sIIIBBBB12s512s415s',
                                self.magic, self.hdrlen, self.expiry, self.codelen,
                                self.vmajor, self.vminor, self.vpatch, self.vbuild,
                                self.reserved1, self.hashes, self.reserved2)
        if sig:
            header += struct.pack('<B64s', self.sigmask, self.sig)
        else:
            header += IMAGE_SIG_SIZE * b'\x00'
        assert len(header) == self.hdrlen
        return header

    def sign(self, sigmask, signature):
        header = self.serialize_header(sig=False)
        data = header + self.code
        assert len(data) == self.hdrlen + self.codelen
        self.sigmask = sigmask
        self.sig = signature

    def write(self, filename):
        with open(filename, 'wb') as f:
            f.write(self.serialize_header())
            f.write(self.code)


class FirmwareImage(BinImage):

    def __init__(self, data, vhdrlen):
        super(FirmwareImage, self).__init__(data[vhdrlen:], magic=b'TRZF', max_size=6 * IMAGE_CHUNK_SIZE)
        self.vhdrlen = vhdrlen
        self.vheader = data[:vhdrlen]

    def write(self, filename):
        with open(filename, 'wb') as f:
            f.write(self.vheader)
            f.write(self.serialize_header())
            f.write(self.code)


class BootloaderImage(BinImage):

    def __init__(self, data):
        super(BootloaderImage, self).__init__(data, magic=b'TRZB', max_size=1 * IMAGE_CHUNK_SIZE)


class VendorHeader(object):

    def __init__(self, data):
        header = struct.unpack('<4sIIBBBBB', data[:17])
        self.magic, \
        self.hdrlen, \
        self.expiry, \
        self.vmajor, \
        self.vminor, \
        self.vsig_m, \
        self.vsig_n, \
        self.vtrust = header
        assert self.magic == b'TRZV'
        assert self.vsig_m > 0 and self.vsig_m <= self.vsig_n
        assert self.vsig_n > 0 and self.vsig_n <= 8
        p = 32
        self.vpub = []
        for _ in range(self.vsig_n):
            self.vpub.append(data[p:p + 32])
            p += 32
        self.vstr_len = data[p]
        p += 1
        self.vstr = data[p:p + self.vstr_len]
        p += self.vstr_len
        vstr_pad = -p & 3
        p += vstr_pad
        self.vimg_len = len(data) - IMAGE_SIG_SIZE - p
        self.vimg = data[p:p + self.vimg_len]
        p += self.vimg_len
        self.sigmask = data[p]
        p += 1
        self.sig = data[p:p + 64]
        assert len(data) == 4 + 4 + 4 + 1 + 1 + 1 + 1 + 1 + 15 + \
                            32 * len(self.vpub) + \
                            1 + self.vstr_len + vstr_pad + \
                            self.vimg_len + \
                            IMAGE_SIG_SIZE
        assert len(data) % 512 == 0

    def print(self):
        print('TREZOR Vendor Header')
        print('  * magic   :', self.magic.decode())
        print('  * hdrlen  :', self.hdrlen)
        print('  * expiry  :', self.expiry)
        print('  * version : %d.%d' % (self.vmajor, self.vminor))
        print('  * scheme  : %d out of %d' % (self.vsig_m, self.vsig_n))
        print('  * trust   :', self.vtrust)
        for i in range(self.vsig_n):
            print('  * vpub #%d :' % (i + 1), binascii.hexlify(self.vpub[i]).decode())
        print('  * vstr    :', self.vstr.decode())
        print('  * vimg    : (%d bytes)' % len(self.vimg))
        print('  * sigmask :', format_sigmask(self.sigmask))
        print('  * sig     :', binascii.hexlify(self.sig).decode())
        print()

    def serialize_header(self, sig=True):
        header = struct.pack('<4sIIBBBBB',
                               self.magic, self.hdrlen, self.expiry,
                               self.vmajor, self.vminor,
                               self.vsig_m, self.vsig_n, self.vtrust)
        header += 15 * b'\x00'
        for i in range(self.vsig_n):
            header += self.vpub[i]
        header += struct.pack('<B', self.vstr_len) + self.vstr
        header += (-len(header) & 3) * b'\x00'  # vstr_pad
        header += self.vimg
        if sig:
            header += struct.pack('<B64s', self.sigmask, self.sig)
        else:
            header += IMAGE_SIG_SIZE * b'\x00'
        assert len(header) == self.hdrlen
        return header

    def sign(self, sigmask, signature):
        if sigmask >= (1 << self.vsig_n):
            raise Exception('signature index is higher than vsig_n (%d)' % self.vsig_n)
        if bin(sigmask).count('1') != self.vsig_m:
            raise Exception('invalid number of indexes (vsig_m expected %d, got %d)' % (self.vsig_m, bin(sigmask).count('1')))
        # sign
        self.sigmask = sigmask
        self.sig = signature

    def write(self, filename):
        with open(filename, 'wb') as f:
            f.write(self.serialize_header())


def binopen(filename):
    data = open(filename, 'rb').read()
    data = bytearray(data)  # python2/3 compatibility
    magic = data[:4]
    if magic == b'TRZB':
        return BootloaderImage(data)
    if magic == b'TRZV':
        vheader = VendorHeader(data)
        if len(data) == vheader.hdrlen:
            return vheader
        subdata = data[vheader.hdrlen:]
        if subdata[:4] == b'TRZF':
            firmware = FirmwareImage(data, vheader.hdrlen)
            # check signatures against signing keys in the vendor header
            if firmware.sigmask > 0:
                pk = [vheader.vpub[i] for i in range(8) if firmware.sigmask & (1 << i)]
                global_pk = ed25519cosi.combine_keys(pk)
                hdr = subdata[:IMAGE_HEADER_SIZE - IMAGE_SIG_SIZE] + IMAGE_SIG_SIZE * b'\x00'
                digest = pyblake2.blake2s(hdr).digest()
                try:
                    ed25519raw.checkvalid(firmware.sig, digest, global_pk)
                    print('Firmware signature OK')
                except:
                    print('Firmware signature INCORRECT')
            else:
                print('No firmware signature')
            return firmware
    if magic == b'TRZF':
        return FirmwareImage(data, 0)
    raise Exception('Unknown file format')


def main():
    if len(sys.argv) < 2:
        print('Usage: binctl file.bin [-s sigmask signature] [-h]')
        return 1
    fn = sys.argv[1]
    sign = len(sys.argv) > 2 and sys.argv[2] == '-s'
    rehash = len(sys.argv) == 3 and sys.argv[2] == '-h'
    b = binopen(fn)
    if sign:
        sigmask = 0
        if ':' in sys.argv[3]:
            for idx in sys.argv[3].split(':'):
                sigmask |= 1 << (int(idx) - 1)
        else:
            sigmask = 1 << (int(sys.argv[3]) - 1)
        signature = binascii.unhexlify(sys.argv[4])
        b.sign(sigmask, signature)
        print()
        b.write(fn)
    if rehash:
        b.update_hashes()
        b.write(fn)
    b.print()


if __name__ == '__main__':
    main()